Conventional methods and devices to build a wireless receiver are generally known. FIG. 1 depicts a block diagram of a conventional wireless receiver 10 that receives data packets. The received signal arrives at antenna 12 and is amplified by low noise amplifier 14 where the output is fed into a phase detector 16 that compares the phase of the received signal with the frequency correction signal 22. The difference is output as phase signal 26, which connects to the automatic frequency correction component 24. The negative feedback provided by the automatic frequency correction component 24 to the phase detector 16 allows the frequency correction process to merge until it matches the rate of the clock embedded in the received transmission. The demodulator 18, bit clock recovery 30, and preamble synch detector 32 play a supporting role in the frequency correction process and may generate additional signals, such as the clock signal 28, to be used by the automatic frequency correction component 24.
The received data packets may be preceded by the reception of noise. Referring to FIG. 2, which is a timing diagram illustrating an example of data packet reception, the received signal starts with purely noise 40, and then a data packet is received. The data packet may begin with a preamble 42 as shown in FIG. 2, which is typically followed by a synchronization field 44 and then the data payload 46. Note that the preamble 42 typically has an embedded clock signal, such as an alternating sequence of zeroes and ones. As part of the reception process, the wireless receiver must merge its clock with clocking information present in the received data packet.
Conventional automatic frequency control suffers from several difficulties. The noise received before a packet may sometimes falsely trigger the automatic frequency correction component 24, which often results in a greater degree of inaccuracy of frequency correction. This can, in turn, result in more error packets. Conventional automatic frequency correction suffers from slow merge times, resulting in more lost packets when the merge is not accomplished before the payload arrives. The wireless receiver must merge its clock with clocking information present in the received data packet quickly, ideally before the end of the reception of the preamble. It must not falsely trigger based on a noise input. A need exists for an improved method and apparatus for automatic frequency correction that addresses these issues.